Cystic fibrosis (CF) is a disorder primarily involving the exocrine glands, and we have begun to study cyclic nucleotides, which may be essential determinants of secretion, in CF. Present topics are: 1) the concentration and distribution of cyclic AMP and cyclic GMP in normal and CF body fluids, 2) the response of cyclic AMP to beta receptor stimulation in normal and CF lymphocytes and fibroblasts, and 3) the response of cyclic GMP to stimulation of the cholinergic receptor in several systems.